Perimeter weighting in iron-type golf clubs distributes non-essential mass of the iron towards the perimeter, reducing the effects that off-center hits have on the golf club and producing more accurate and consistent golf ball trajectories. Perimeter weighting is achieved by creating a cavity in the back of the golf club opposite the face or hitting surface. The material weight removed to create this cavity is redistributed around the perimeter of the golf club head. In general, larger cavity volumes correspond to increased amounts of mass distributed around the perimeter.
Removing material from the rear of the club head, however, reduces the thickness of the club face. Since the club face is the hitting surface, the club face cannot be so thin that the strength of the club face surface is not sufficient to withstand the stress resulting from a golf ball striking the club face. Reducing the thickness of the club face may also increase vibrations upon impact. These vibrations may cause bad feel to the user.
There are various examples of secondary material incorporation into iron golf club heads for vibration damping. Some of these examples have provided the additional benefit of displacing weight to the perimeter of the club head so as to increase the club head's rotational moment or inertia (MOI). These vibration dampers, however, have involved multiple materials such as in constrained layer damping, or they have been positioned across the entire face or isolated to the lower area of the club head. In addition, most conventional club heads are made of one homogenous material and the secondary damping materials incorporated into the golf club head are also homogenous. This type of construction, however, imposes design constraints on the head configuration, thus limiting the opportunity to produce an iron with forgiving play characteristics while at the same time maintaining a traditional sized head. The use of one homogenous material also may limit the placement of the head's center of gravity.
Therefore, a golf club head is desired that utilizes a secondary material to improve vibration damping while improving the placement of the center of gravity and MOI of the club head to improve golf ball launch conditions and to improve the feel of the club to the user.